Interpretive Summary: The importance of adequate vitamin D intake for bone health is well recognized. Vitamin D may play important roles in oral health, colon cancer, and autoimmune disease. Even though vitamin D can be formed in the skin by exposure to sunlight, dietary sources are needed when exposure is limited. In the U.S., since the 1930’s, most milk and milk products have been fortified with vitamin D. The U.S. Food and Drug Administration requires that fortified milk have a vitamin D content of at least 400 IU (10 µg)/quart up to a maximum of 600 IU (15 µg)/quart based on good manufacturing practices. This wide tolerance means the actual vitamin D3 content of an individual carton of milk can vary appreciably from the labeled value. In order to make an accurate estimate of vitamin D3 in fortified milk in the U.S., skim, 1% fat, 2% fat, whole, and 1% fat chocolate milk samples were collected from 24 different statistically selected supermarkets. These samples were analyzed for vitamin D3 using validated methodology. The average value for all the sample types was 462 IU (11.6 µg)/quart with the averages for the different types of milk ranging from 417 to 498 IU(10.4 to 12.4 µg). These data have been used to update and improve food composition data in the United States Department of Agriculture (USDA) National Nutrient Database for Standard Reference (SR). Vitamin D content of milk and of more than 3000 other foods were released in SR 22 (2009); SR is the primary source of nutrient information used when estimating the nutrient intake of the U.S. population.

Technical Abstract:
The vitamin D3 content and variability of retail milk in the United States, having a declared fortification level of 400 IU (10 µg) per quart (25% DV per 8 fl oz serving), was determined. In 2007, vitamin D3 fortified milk (skim, 1% fat, 2% fat, whole, and 1% fat chocolate milk) was collected from 24 different statistically selected supermarkets in the U.S. Additionally, 2% fat milk samples from an earlier 2001 USDA nationwide collection were re-analyzed. Vitamin D3 was determined using a specific validated method involving HPLC with ultraviolet spectroscopic detection, and vitamin D2 as an internal standard. Quality control materials were analyzed with the samples. Of the 120 milk samples procured in 2007, 49% had vitamin D3 within 100 to 125% of 400 IU (10 µg)/qt (label value), 28% had 501-600 IU (12.6-15 µg)/qt, 16% had a level below the label amount, and 7% had >600 IU (15 µg)/qt (>150% of label). Whereas the mean vitamin D3 content did not differ statistically between milk types, there was a wide range in values among individual samples, from non-detectable (<20 IU [0.5 µg]/qt) for one sample to nearly 800 IU (20 µg)/qt, with a trend toward more samples of whole milk having >150% of the labeled content. On average, vitamin D3 in 2% milk was higher in 2007 compared to 2001 (473 vs. 426 IU [11.8 vs. 10.6 µg]/qt).